Today astronomers announced that they have reached an all-time low --
low temperatures, that is. Adam Burgasser and Davy Kirkpatrick at the
California Institute of Technology in Pasadena, CA, have identified the coolest
body ever imaged outside of the solar system, a brown dwarf that lies only 19
light years from the Earth.

"Brown dwarfs are essentially failed stars," explains Burgasser, a
Caltech physics graduate student who is heading up the investigation of these
objects as his doctoral thesis project. "They are too small to ignite nuclear
reactions in their cores, so they simply fade with time."

This newest brown dwarf discovery was imaged by the Two Micron All Sky
Survey (2MASS), a project whose goal is to image the entire sky at near-infrared
wavelengths. 2MASS is a collaborative effort between the University of
Massachusetts and Caltech's Infrared Processing and Analysis Center (IPAC).
Optical photographs obtained as part of the first-generation Palomar Observatory
Sky Survey (POSS-I) were converted into digitial form at the U. S. Naval
Observatory in Flagstaff, Arizona, and compared against the 2MASS data. This
comparison revealed that the object had no associated optical counterpart,
implying that it was most likely a very cool object shining primarily at near-
infrared wavelengths. Burgasser confirmed the object's status as a brown
dwarf by taking its spectral "fingerprint" using a spectrograph constructed by
The Ohio State University at the National Science Foundation's 4-meter (160-
inch) Victor M. Blanco telescope. This telescope is located at the Cerro Tololo
Interamerican Observatory (CTIO) outside of La Serena, Chile.

The 2MASS discovery image, taken in 1998 during routine survey
operations from the 2MASS southern observatory also located at Cerro Tololo,
Chile, showed that the brown dwarf lay in close proximity to a nearby triple
star system called Gliese 570ABC, located in the constellation Libra. A second
2MASS image taken 14 months later confirmed that the brown dwarf was in fact a
previously undetected fourth member of this system. "Gliese 570ABC moves across
the sky very slightly every year, undetectable with the naked eye but detectable
with a telescope. The triple star and the brown dwarf moved the same distance
and in the same direction, which means that they are part of the same stellar
family," said Burgasser.

Using the known distance to Gliese 570ABC and the brightness of the
brown dwarf itself, Burgasser and Kirkpatrick, senior staff scientist at IPAC
and a member of the 2MASS team, computed that the object's temperature must be
only 500 degrees Celsius (900 degrees Fahrenheit), or just one and a half times
warmer than the maximum setting on a conventional kitchen oven. "This makes it
the coolest star-like object ever imaged beyond our Solar System," says
Kirkpatrick.

The spectral "fingerprint" that Burgasser obtained shows that the brown
dwarf contains methane as well, a trait also shared by planets such as Jupiter
and Saturn but not by stars. Although the new discovery, now dubbed Gliese
570D, shows methane and is believed to be roughly the same size as Jupiter
itself, it is believed to be roughly 50 times more massive. "The dividing line
between planets and stars was once obvious," says Burgasser, "but we are now
finding objects that really blur that distinction."

The 2MASS telescopes are in the midst of a 3-1/2-year survey of the
entire sky. IPAC's processing of the 20 terabytes of raw survey data will
create a publicly accessible catalog of 300 million stars and over one million
galaxies. Already, 6% of the sky -- more than 20 million objects -- has been
released to the public. Nearly one-half of the sky -- almost 200 million
objects -- will be publicly available early in 2000. The 2MASS project is based
at the University of Massachusetts, Amherst. The JPL/Caltech Infrared
Processing and Analysis Center combines and processes 2MASS images into usable
data and serves those catalogs and images to the public.

As part of NASA's Origins Program, 2MASS is funded by NASA's Office of
Space Science and the National Science Foundation. Results from 2MASS will
benefit future Origins missions, including Space Infrared Telescope Facility and
the Next Generation Space Telescope. JPL manages the program for NASA's Office
of Space Science, Washington, DC. JPL is a division of the California Institute
of Technology, Pasadena, CA.

CTIO is a division of the National Optical Astronomy Observatories
(NOAO). NOAO is operated by the Association of Universities for Research in
Astronomy (AURA), Inc., under co-operative agreement with the National Science
Foundation.

CAPTION TO INCLUDED IMAGE: (a) In the left panel are Two Micron All Sky Survey
(2MASS) images of three objects. These are false-color images generated by
mapping the three near-infrared wavelengths at which 2MASS observes into blue,
green, and red colors. The first 2MASS image (top left) shows a methane brown
dwarf (also called a "T dwarf"). Below that are 2MASS images of Uranus with its
five major moons and Neptune with its largest moon, Triton. Strong methane
absorption causes the T dwarf, Uranus, and Neptune all to appear blue in these
images. (b) In the right panel is an artist's rendition in visible light of the
Gliese 570ABCD system. In the upper right corner of this image are the three
cool stars (one yellow and the other two red) comprising the core of the system.
Below them is shown the cool brown dwarf ("T dwarf") companion, Gliese 570D,
an even cooler object which is depicted here as having a reddish, banded
atmosphere. A dark, hypothetical companion to this brown dwarf is also shown.

PHOTO CREDIT: (Left Panel): 2MASS images courtesy of the University of
Massachusetts and the Infrared Processing and Analysis Center. (Right Panel):
Artist's rendition by Dr. Robert Hurt of the Infrared Processing and Analysis
Center.